The present invention relates to a roofing product. More specifically, the present invention is directed to a roof covering member possessing thermal expansion relief characteristics.
Roofing shingles are commonly used to provide a protective environmental barrier layer for a pitched roof. These shingles typically include asphalt shingles, non-asphalt engineered composite shingles, wood shake singles, slate shingles, ceramic and concrete tiles and the like. Engineered composite shingles have become popular for commercial and residential installations in recent years due to their high strength and durability, lower cost and maintenance as compared to wood and slate shingles, and relative ease of installation. Because of their composite nature, engineered composite shingles can be fabricated to imitate the look of shake, slate, tile, and many other types of shingles. One particular type of composite shingle employs a material makeup of at least a polymer component and a filler component. For instance, the polymer component may comprise one or more thermoplastic materials and the filler component may comprise one or more minerals, as examples. Coloring agents, UV inhibitors, stabilizers, and other additives may be added or applied to the material makeup to improve the characteristics of the finished shingle product.
When installing a shingled roof covering system on a pitched roof, a starter course, or row, is usually coupled to a roof deck along the eaves to form a base for the first course of full shingles. Additional shingle courses are applied to partially overlap the previous courses as the roofing installer works their way up to the ridgeline.
One particular problem faced by shingle installers is how to account for thermal expansion and contraction cycles that occur when singles are exposed to temperature extremes in the outdoor environment. This is especially problematic when a semi-rigid to rigid shingle has fixed point of attachment on a building roof structure and will become exposed to temperatures that vary greatly from the temperature of the shingle when it is installed on the roof, such a temperature differential being referred to herein as “Delta T”. As one example, consider the pair of shingles 100 illustrated in FIG. 1 as positioned adjacent to one another in the same course on a roof deck (not shown). A fastener is inserted through one of a set of nailing zones 102 on the shingle top surface 103 and into the roof deck to rigidly affix the shingle 100 onto a building. Because these shingles 100 have side regions 104 that abut one another when installed, any thermal expansion of the shingles will cause each to expand laterally and the side regions 104 of each shingle to exert a sizeable force on the side region of the adjacent shingle. Moreover, a large Delta T causes a bowing or “pillowing” effect of the shingles 100 where a mid-region of the shingle moves upwardly off of the underlying roof deck. This bowing effect can undermine the attachment of the fasteners extending through the nailing zones 102, potentially causing them to move out of engagement with the roof deck. Additionally, the bowing can leave areas of the underlying roof deck directly exposed to the environment, which could allow precipitation and other elements to infiltrate the structure of the roof. Furthermore, the bowing diminishes the aesthetics of the roofing product.
Therefore, it would be beneficial to provide a roofing product that possesses thermal expansion relief characteristics, particularly for handling situations where the product is exposed to ambient temperatures that vary significantly from the temperatures at product installation.